Sturdy, Compact, Collapsible Camping Chair with a Central Tube Connector

ABSTRACT

A collapsible chair includes upper tubes, leg tubes, a tube connector and a seat back. The connector has four tubes bent in U shapes. Two bent tubes are welded to each other at the bottoms of the U shapes, and another two bent tubes are inverted and welded to each other at the tops of the inverted U shapes. The arms of the four U shapes are welded to each other. Upper holes are formed by ends of the first bent tubes, and lower holes are formed by ends of the second bent tubes. Lower ends of the upper tubes are inserted into the upper holes, and upper ends of the leg tubes are inserted into the lower holes. Upper ends of the upper tubes fit into tube receptacles in the seat back. The two back upper tubes are bent and are longer than the two straight front upper tubes.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and hereby claims the benefit under 35 U.S.C. §119 from Korean Patent Application No. 2020140008443, filed on Nov. 18, 2014, in the Republic of Korea, the subject matter of which is incorporated herein by reference. This application is a continuation-in-part of Korean Application No. 2020140008443. In addition, this application is a continuation-in-part of, and claims priority under 35 U.S.C. §120 from, nonprovisional U.S. patent application Ser. No. 29/507,311 entitled “Collapsible Chair with a Central Hub of Crossed Poles,” filed on Oct. 27, 2014, the subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

The described embodiments relate to chairs, and more particularly to portable, collapsible chairs that are suitable for camping, fishing, outdoor concerts and sporting events.

BACKGROUND

Portable chairs are convenient during outdoor activities at which seating is otherwise unavailable. Folding chairs that are commonly used in the home to save space are not sufficiently portable for most outdoor activities, such as camping, hiking, fishing, outdoor concerts and sporting events. A portable chair for outdoor activities should be light weight and compact. For example, a chair used for hiking or camping should advantageously fit into a back pack and not weigh down the hiker. The typical tube-and-canvas folding chairs used at field-side sporting events are simply too large and heavy to take along on a hike. A smaller and lighter folding chair would also be more convenient even at events on a field that is a short distance from the trunk of the user's car.

FIG. 1 (prior art) shows an unfolded, light-weight, collapsible chair 10 that is appropriate for hiking and camping. Chair 10 includes ten poles that pivot in molded-plastic pole connectors. Three poles pivot in each of the two back bottom pole connectors 11-12, and two poles pivot in each of the two front bottom pole connectors 13-14. Two poles also pivot in each of the two front top pole connectors 15-16. Two poles pivot in each of the two back top pole connectors 17-18, which slide along the two longer poles 19-20 that support the seat back. The two longer poles 19-20 are inserted into corner pockets of the seat cover 21, which is attached at the front to the two front top pole connectors 15-16.

FIG. 2 (prior art) shows collapsible chair 10 of FIG. 1 in a folded state. The poles have been folded together so that they fit together with the seat cover 21 into a carrying bag 22. However, chair 10 in carrying bag 22 is still relatively bulky. Especially the two longer poles 19-20 that support the back of the chair are several feet long and much too long to fit into a back pack. So the bag 22 must be carried separately. Moreover, the collapsible chair 10 is not sturdy. The front corners of the seat cover 21 have only diagonal support from poles that are longer than conventional chair legs. The weight of the occupant of the chair is more likely to bend the longer poles. And the two longer back support poles 19-20 are also more likely to bend under the weight of the chair occupant. Finally, the poles are likely to separate from the plastic pole connectors 11-18 because the poles are pivotally attached to the connectors only by small metal pins.

A collapsible camping chair is sought that is light-weight and compact but nevertheless sturdy and durable.

SUMMARY

A sturdy, compact collapsible chair includes upper tubes, leg tubes, a central tube connector and a fabric seat back. All of the tubes are hollow and metal. The tube connector has two first short tubes and two second short tubes bent in U shapes. The first tubes are welded to each other at the bottoms of the U shapes, and the second tubes are inverted and welded to each other at the tops of the inverted U shapes. The arms of the U shapes of the first tubes are welded to arms of the U shapes of the second tubes at four locations. Upper holes are formed by the ends of the first tubes, and lower holes are formed by the ends of the second tubes. The upper tubes are formed from detachable sections. Each of the back upper tubes has an upper section, a middle section and a lower section. Each front upper tube has an upper section and a lower section. No part of the upper tubes other than the upper and lower ends contacts any part of the chair.

The lower end of each upper tube is inserted into one of the upper holes in the first bent tubes, and the upper end of each of the leg tubes is inserted into one of the lower holes in the second bent tubes. Each of the lower ends of the upper tubes has a circular cross section that is dimensioned to fit snugly into the circular circumference of a corresponding upper hole. Upper ends of the upper tubes fit into tube receptacles in the seat back. No part of the upper tubes other than the upper and lower ends contacts any part of the collapsible chair. The two back upper tubes are longer than the two front upper tubes. The lower section of each of the two back upper tubes is curved, whereas both sections of each front upper tube are straight.

A method of manufacturing the sturdy, collapsible chair includes forming tubes, a central tube connector and a seat back and then placing the tubes, connector and seat back in a bag that is less than one foot long. A plurality of upper tubes are formed in detachable sections. Each back upper tube has an upper section, a middle section and a lower section. The upper and middle sections are straight, whereas the lower section is bent. Each front upper tube has a straight upper section and a straight lower section. The upper tubes have lower ends and seat ends. A plurality of leg tubes are formed with upper ends and ground ends. The lower ends of the upper tubes and the upper ends of the leg tubes have outer diameters that are dimensioned to fit snugly into the inner diameters of the regular tube dimensions.

The central tube connector is formed by bending first short tubes and second short tubes into U shapes. The two first bent tubes are welded to each other at the bottoms of the U shapes such that four upper holes with circular circumferences are disposed at ends of the first tubes. The circular cross sections of the lower ends of the upper tubes are dimensioned to fit snugly into the circular circumferences of the upper holes. The two second bent tubes are welded to each other at the bottoms of the U shapes and then inverted such that four lower holes with circular circumferences are formed at the ends of the second bent tubes. The upper ends of the leg tubes are dimensioned to fit snugly into the lower holes of the second short bent tubes. The arms of the U shapes of the first short tubes are welded to the arms of the U shapes of the inverted second short tubes to form the central tube connector with only six welds.

An elastic cord is pulled through each of the tubes. An elastic cord is passed from each front upper tube, through an upper hole, through a first bent tube, out another upper hole and into the other front upper tube. An elastic cord also passes from each back upper tube, through an upper hole, through the other first bent tube, out another upper hole and into the other back upper tube. Similarly, an elastic cord passes from each front leg tube, through a lower hole, through a second bent tube, out another lower hole and into a back leg tube. The seat back is made with four tube receptacles disposed at locations on the seat back so as to fit over the seat ends of the upper tubes.

Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

FIG. 1 (prior art) is a perspective view of a collapsible chair with long poles that pivot in plastic pole connectors.

FIG. 2 (prior art) shows the collapsible chair of FIG. 1 in a folded state and in a carrying bag.

FIG. 3 is a perspective view of an assembled sturdy, collapsible chair according to the present invention.

FIG. 4 is a perspective view of the central tube connector of the chair of FIG. 3 made with four bent tubes.

FIG. 5 shows the central tube connector of FIG. 4 from a different perspective.

FIG. 6 shows the frame of the chair of FIG. 3 in the collapsed state in the process of being assembled.

FIG. 7 shows the tubes of the frame of the chair of FIG. 3 bunched up parallel to one another to be placed in a bag.

FIG. 8 is a perspective view of the chair of FIG. 3 in the assembled state before the seat back is placed over the upper tubes.

FIG. 9 shows an occupant sitting in the assembled collapsible chair of FIG. 3.

FIG. 10 is a flowchart of steps of a method of manufacturing the collapsible chair of FIG. 3.

FIG. 11 is a perspective view of another embodiment of the central tube connector of FIG. 4 in which the four short bent tubes have been replaced with a unitary molded piece.

FIG. 12 shows the unitary central tube connector of FIG. 11 from above.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings. In the description and claims below, terms such as “upper”, “top”, “up”, “down”, “lower”, “bottom”, “over” and “under” are used herein to describe relative orientations between different parts of the structure being described, and it is to be understood that the overall structure being described can actually be oriented in any way in three-dimensional space.

FIG. 3 shows a sturdy, compact, collapsible chair 30 in an assembled state. Collapsible chair 30 can easily be disassembled and placed in a small bag that is less than a foot long. Collapsible chair 30 consists of four upper tubes 31-34, four leg tubes 35-38, a central tube connector 39, four elastic cords with associated plugs, and a seat back 40. The upper tubes 31-34 and leg tubes 35-38 are hollow tubes with circular cross sections. The back two upper tubes 33-34 are longer than the front two upper tubes 31-32. The front two upper tubes 31-32 have detachable upper and lower sections, while the back two upper tubes 33-34 have detachable upper, middle and lower sections. The central tube connector 39 has two first short bent tubes 41-42 and two second short bent tubes 43-44. In one embodiment, the upper tubes 31-34, the leg tubes 35-38, the two first bent tubes 41-42, and the two second bent tubes 43-44 are all made of aluminum, which is light weight but yet strong. Thus, the light-weight, compact, collapsible chair 30, which fits into a small bag, is suitable especially for hiking and camping. In another embodiment, all of the tubes are made of steel, with is heavier but stronger than aluminum.

The leg tubes 35-38, the sections of the upper tubes 31-34, the first bent tubes 41-42, and second bent tubes 43-44 all have the same diameter. In one embodiment, the tubes have an outer diameter of one half inch. One end of each of the leg tubes 35-38 and each section of the upper tubes 31-34 has a smaller outside diameter that fits inside the inner diameter of the regular tube dimensions. For example, the lower end of the lower section of the upper tube 31 has a one-inch length with a three-eighths-inch outer diameter that fits inside the inner diameter of the first bent tube 41.

FIG. 4 is a perspective view of the central tube connector 39 in more detail. The central tube connector 39 is formed by bending each of the four first and second short tubes 41-44 to form a wide “U”. The angle between the arms of the “U” is slightly less than ninety degrees. Then the four tubes 41-44 are welded together at only six locations. The U shapes of the first bent tubes 41-42 open upwards such that upper holes 45-48 with circular circumferences are disposed at the ends of the first tubes 41-42. For example, upper holes 45-46 are at the ends of first short tube 41. The bottoms of the U shapes of first tubes 41-42 are welded to each other. After welding, the angle between the planes of the U shapes is about ninety degrees. FIG. 4 shows the weld 49 between the bottoms of the U shapes of first tubes 41-42.

The U shapes of the second bent tubes 43-44 are inverted to open downwards. The bottoms of the two inverted U shapes of the two second tubes 43-44 are welded to each other such that four lower holes with circular circumferences are formed at the ends of the second tubes 43-44. The angle between the planes of the U shapes of the welded second tubes 43-44 is also about ninety degrees. FIG. 4 shows the weld 50 between the bottoms of the inverted U shapes of second tubes 43-44. The arms of the U shapes of the first tubes 41-42 are welded to the arms of the U shapes of the inverted second tubes 43-44 such that the arms of the second tubes 43-44 are welded to the insides of the arms of the first tubes 41-42. The first tubes 41-42 are welded to the second tubes 43-44 at only four locations 51-54. Thus, the central tube connector 39 is formed by welding the four short bent tubes at only six locations. Welding the tubes of the central tube connector at only six locations results in a simple, inexpensive but yet sturdy design.

FIG. 4 shows the two upper holes 45-46 with circular circumferences at the ends of the first short bent tube 41. The upper tubes 31-34 have lower ends and seat ends, and the leg tubes 35-38 have upper ends and bottom ends. FIG. 4 shows the lower end 55 of the lower section of the upper tube 31 and the lower end 56 of the lower section of the upper tube 32. The circular cross sections of the lower ends of the upper tubes 31-34 are dimensioned to fit snugly into the circular circumferences of the upper holes 45-48. Similarly, the upper ends of the leg tubes 35-38 are dimensioned to fit snugly into the lower holes. To assemble the collapsible chair 30, the lower ends of the upper tubes 31-34 are detachably connected to the first tubes 41-42 by being inserted into the upper holes 45-48. For example, the lower end 55 of upper tube 31 is inserted into upper hole 45 of first tube 41, and the lower end 56 of upper tube 32 is inserted into upper hole 46 of first tube 41. Similarly, to assemble the collapsible chair 30, the upper ends of the leg tubes 35-38 are detachably connected to the second tubes 43-44 by being inserted into the lower holes.

FIG. 5 shows the central tube connector 39 looking between the first tubes 41-42 on the bottom and the second tubes 43-44 on the top. FIG. 5 shows how the two first short bent tubes 41-42 have U shapes, and the second short bent tubes 43-44 have inverted U shapes slanting downwards. The ninety-degree angle is indicated between the planes of the U shapes of the welded second tubes 43-44.

FIG. 6 shows the frame 57 of collapsible chair 30 in the collapsed state. The frame is made entirely of metal tubes. Thus, no additional manufacturing equipment or processes are required to work with materials other than the hollow metal tubing. For example, no molds are required to make the plastic pole connectors 11-18 of the collapsible chair 10 of the prior art. The tubes themselves are used as a means for forming the holes into which the ends of other tubes are detachably connected to assemble the collapsible chair 30. FIG. 6 shows that the shorter front two upper tubes 31-32 have detachable upper and lower sections, while the back two upper tubes 33-34 have detachable upper, middle and lower sections. For example, front upper tube 32 has an upper section 58 and a lower section 59, and back upper tube 33 has an upper section 60, a middle section 61 and a lower section 62. The seat ends of the upper tubes 31-34 are opposite the lower ends 55, 56, 63 and 64 that fit snugly into the upper holes 45-48, respectively. The circular cross section of each of the lower ends 55, 56, 63 and 64 is dimensioned to fit snugly into the circular circumference of the corresponding upper hole 45-48.

Returning to FIG. 3, the seat ends of the upper tubes 31-34 are shown detachably connected to the tube receptacles 65-68, respectively, at the four corners of the seat back 40. The seat back 40 is made of stitched pieces of woven fabric, such as canvas. The seat back 40 is stretched so that the tube receptacles 65-68 will fit over the seat ends of the upper tubes 31-34. The curved back upper tubes 33-34 can have only one orientation in the upper holes and still fit into the tube receptacles 65-68. Thus, in the assembled state, the upper tubes 31-34 are under some tension that pulls the seat ends together. In one embodiment, the tube receptacles 65-68 are pockets sewn in the fabric of the seat back 40. In another embodiment, the tube receptacles 65-68 are hard plastic cylinders into which the seat ends of the upper tubes 31-34 slide. The plastic cylinders are either glued or stitched to the fabric of the seat back 40. In the assembled state of collapsible chair 30, no part of the upper tubes 31-34 other than the lower ends and the seat ends contacts any part of the collapsible chair. The bottom ends of the leg tubes 35-38 rest on the ground.

FIG. 7 shows the upper tubes 31-34, the leg tubes 35-38 and the central tube connector 39 in the collapsed state bunched up to be placed in a bag. Because each of the tube sections is less than one foot long, the entire collapsible chair 30 can fit into a bag that is less than one foot long. The collapsed tubes of the frame 57 are rolled up in the seat back 40 before being inserted into the bag. In the collapsed state of FIG. 7, all of the tubes 31-38 have been pulled out of the holes in the central tube connector 39. In addition, the sections of the upper tubes 31-34 have been pulled apart. Elastic cords pass through all of the upper tubes, leg tubes, first bent tubes and second bent tubes. When the tubes of the frame 57 are removed from their bag, the elastic cords tend to pull the tube sections into one another and the upper tubes and leg tubes into the holes in the first bent tubes and the second bent tubes. The user can then align the tube sections with each other and with the upper and lower holes, and the tubes are pulled into the central tube connector 39. Thus, the elastic cords tend to pull the tubes of the frame 57 into the assembled state. Once in the assembled state, the tubes are held in place by the elastic cords.

The ends of the elastic cords are attached to the inside of plugs that fit into the seat ends of the upper tubes 31-34 or into the bottom ends of the leg tubes 35-38. One elastic cord passes from an end plug at the seat end of front upper tube 31, through first bent tube 41 and through front upper tube 32 to an end plug at the seat end. A second elastic cord passes from an end plug at the seat end of back upper tube 33, through first bent tube 42 and through back upper tube 34 to an end plug at the seat end. A third elastic cord passes from a ground plug at the bottom end of front leg tube 35, through second bent tube 43 and through back leg tube 38 to a ground plug at the bottom end. Finally, a fourth elastic cord passes from a ground plug at the bottom end of front leg tube 36, through second bent tube 44 and through back leg tube 37 to a ground plug at the bottom end. Thus, there are four elastic cords that each pass through the means 41-44 for forming the upper and lower holes. For example, portions of an elastic cord 69 can be seen in FIG. 7 coming out of hole 46 in first bent tube 41 and passing into front upper tube 32. Cord 69 can also be seen coming out of hole 45 at the other end of first bent tube 41 and passing into front upper tube 31. FIG. 4 also shows cord 69 passing from front upper tube 32 into hole 46 in first bent tube 41 and out of hole 45 and into front upper tube 31.

FIG. 8 is a perspective view of the frame 57 of collapsible chair 30 in the assembled state before the tube receptacles at the corners of the seat back 40 have been slipped over the seat ends of the upper tubes 31-34. FIG. 8 shows that the back upper tubes 33-34 with three sections have a first length that is longer than the second length of the front upper tubes 31-32, which have only two sections. The longer back upper tubes 33-34 support the back of the seat back 40, whereas the shorter front upper tubes 31-32 support the seat of the seat back 40 upon which the user's legs rest. The lower sections 62 and 70 of each of the back upper tubes 33 and 34 are curved, whereas the middle and upper sections of the back upper tubes 33 and 34 are straight. By curving the back upper tubes 33, 34 upwards at the lower sections 62, 70, the seat ends 71, 72 of the back upper tubes are moved forward closer to the central tube connector 39, and the center of gravity of the occupant of collapsible chair 30 is moved in front of the central tube connector 39. Thus, bending the lower sections 62, 70 allows the center of gravity to be in front of the central tube connector 39 even through the back upper tubes 33-34 that support the back of the seat are significantly longer than the front upper tubes 31-32. The occupant of collapsible chair 30 is less likely to fall backwards than if the chair had entirely straight back upper tubes. In addition, bending the lower sections 62, 70 moves the back upper tubes 33, 34 away from the bottom of the seat back 40, which is pressed down by the occupant. It would be uncomfortable for the occupant to feel the back support tubes when sinking into the chair if the back support tubes were entirely straight.

FIG. 9 shows an occupant 73 sitting in the assembled collapsible chair 30. FIG. 9 illustrates that the center of gravity of the occupant 73 is in front of the central tube connector 39 even though the occupant is resting on the back of the seat. Moreover, the bent lower sections 62, 70 remain a significant distance away from the bottom of the seat back 40 that is pressed down by the occupant 73. Even if the seat back 40 were lower slung than in FIG. 9, the bent lower sections 62, 70 would still prevent the back upper tubes 33-34 from pressing against the occupant 73. The first bent tubes 41-42 and the second bent tubes 43-44 are metal welded to each other to form the central tube connector 39 and are therefore stronger than the plastic pole connectors 11-18 of prior art chair 10 at holding the tubes in place.

FIG. 10 is a flowchart illustrating steps 75-83 of a method of manufacturing collapsible chair 30. In a first step 75, the detachable sections of the upper tubes 31-34 are formed from hollow metal tubes with circular cross sections. The metal can be aluminum or steel. Each of the sections of the upper tubes 31-34 has a lower end with a smaller outer diameter. The lower end of each tube section is dimensioned to fit snugly into the hole formed by the end of the tube below. For example, the lower end of the upper section 60 of tube 33 is dimensioned to fit snugly into the hole at the top of the middle section 61. Similarly, the lower end of the middle section 61 of tube 33 is dimensioned to fit snugly into the hole at the top of the lower section 62. The lower end of lower section 62 is the lower end of upper tube 33.

In step 76, the leg tubes 35-38 are also formed from hollow metal tubes with the same diameter as the upper tubes 31-34. Each leg tube has only a single section. The leg tubes 35-38 have upper ends and lower ground ends. At the upper ends of the leg tubes 35-38 there is an upper portion that has a smaller outer diameter than the rest of the leg tubes.

In step 77, the first short tubes 41-42 and the second short tubes 43-44 are bent into U shapes. The arms of the U shapes open at an angle of somewhat less than ninety degrees, such as eighty-five degrees. The upper holes 45-46 have circular circumferences and are disposed at the ends of the first tube 41, and the upper holes 47-48 have circular circumferences and are disposed at the ends of the first tube 42. The circular cross sections of the lower ends of the upper tubes 31-34 are dimensioned to fit snugly into the circular circumferences of the upper holes 45-48. Lower holes with circular circumferences are disposed at the ends of the second tubes 43-44. The circular cross sections of the upper ends of the leg tubes 35-38 are dimensioned to fit snugly into the circular circumferences of the lower holes.

In step 78, the two first short tubes 41-42 are welded to each other at location 49 at the bottoms of the U shapes such that the upper holes 45-48 face upwards. The angle between the plane of the U shape of first tube 41 and the U shape of first tube 42 is about ninety degrees.

In step 79, the two second short tubes 43-44 are welded to each other at the location 50 at the bottoms of the U shapes. The two welded second tubes 43-44 are then inverted upside down such that the four lower holes at the ends of the second tubes face downwards.

In step 80, the four arms of the two U shapes of the first tubes 41-42 are welded to the four arms of the U shapes of the two inverted second tubes 43-44. Thus, the first tubes 41-42 are welded to the second tubes 43-44 at only the four locations 51-54.

In step 81, the seat back 40 is made with the four tube receptacles 65-68 disposed at the corners of the approximately rectangular seat back so as to fit over the seat ends of the upper tubes 31-34. The seat back 40 is made by stitching together various pieces of fabric or plastic. The tube receptacles 65-68 can be sewn as pockets into the seat back or they can be molded plastic cylinders that are glued or stitched to the corners of the seat back 40.

In step 82, an elastic cord is pulled through each front pair and back pair of upper tubes and each front and back pair of leg tubes. The two elastic cords that pass through the front pair and the back pair of upper tubes also pass through the first short bent tubes 41-42. The two elastic cords that pass through each pair of front and back leg tubes also pass through the second short bent tubes 43-44. For example, the elastic cord 69 attaches to an end plug 84 at the seat end of front upper tube 31 and is pulled through the tube 31, into upper hole 45, through the first short tube 41, out of upper hole 46, into the front upper tube 32 and attaches to an end plug at the seat end of tube 32. A second elastic cord attaches to an end plug 85 at the seat end 71 of back upper tube 33 and is pulled through the sections of tube 33, into upper hole 47, through first short bent tube 42, out upper hole 48, through the sections of back upper tube 34 and attaches to an end plug at the seat end of tube 34. Similarly, a third elastic cord that attaches to a ground plug of leg tube 35 is pulled through tube 35, into a lower hole, through second short bent tube 43, out another lower hole, through back leg tube 38 and attaches to a ground plug at the bottom end of tube 38. Finally, a fourth elastic cord passes from front leg tube 36, through second tube 44 and through back leg tube 37.

In step 83, the upper tubes 31-34, the leg tubes 35-38, the first tubes 41-42, the second tubes 43-44 and the seat back 40 are placed in a bag that is less than one foot long. All of the tube sections of the upper tubes are first detached from one another, and the tubes are detached from central tube connector 39. The tubes are then oriented relatively parallel to one another, as shown in FIG. 7. The tubes are then rolled up in the seat back 40, and the upper tubes 31-34, the leg tubes 35-38, the first short bent tubes 41-42, the second short bent tubes 43-44 and the seat back 40 are placed in the bag. Because each of the tube sections and the leg tubes is less than twelve inches long, the components of collapsible chair 30 fit in a bag that is less than a foot long, which is ideal for camping and hiking. The bag is less than six inches in diameter.

To assemble the collapsible chair 30, the user removes the tubes and the seat back 40 from the bag and unwraps the seat back from around the tubes. The user then aligns the tube sections with each other and with the upper and lower holes. The elastic cords tend to pull the tube sections into one another and the upper tubes into the upper holes in the first bent tubes. The elastic cords also pull the leg tubes into the lower holes in the second bent tubes. The back upper tubes 33-34 are formed when the upper sections are detachably connected to the middle sections, and the middle sections are detachably connected to the lower sections. The front upper tubes 31-32 are formed when the upper sections are detachably connected to the lower sections. To assemble the collapsible chair 30, the lower ends of the upper tubes 31-34 are detachably connected to the first tubes 41-42 by being inserted into the upper holes 45-48, and the upper ends of the leg tubes 35-38 are detachably connected to the second tubes 43-44 by being inserted into the lower holes.

FIG. 11 shows another embodiment of the frame 57 of collapsible chair 30 in which the two first short tubes 41-42 and the two second short tubes 43-44 have been replaced with a unitary central tube connector 86. Central tube connector 86 is molded in one-piece and is either die-cast metal or injection-molded, reinforced plastic. The reinforced plastic is embedded with fibrous matter, such as carbon fiber, in order to confer additional strength to the plastic. The upper tubes 31-34 and leg tubes 35-38 are inserted into upper holes and lower holes in central tube connector 86 in the same manner as the tubes are inserted into central tube connector 39.

FIG. 12 is a top view of the unitary central tube connector 86 of FIG. 11. Connector 86 is more compact and smaller than the first and second tubes 41-44 of central tube connector 39. The upper holes and lower holes in central tube connector 86 are spaced closer together than are the corresponding holes in central tube connector 39. Thus, central tube connector 86 has a plurality of upper holes into which the lower ends of the upper tubes 31-34 are detachably connected by being inserted into the upper holes. Each of the upper holes 45-48 has a circular circumference, and each of the lower ends of the upper tubes 31-34 has a circular cross section such that there is no space between the lower ends of the upper tubes 31-34 and the circumference of the upper holes 45-48 when the lower ends of the upper tubes are inserted into the upper holes. Similarly, the upper ends of the leg tubes 35-38 are detachably connected to the central tube connector 87 by being inserted into the lower holes.

Although certain specific exemplary embodiments are described above in order to illustrate the invention, the invention is not limited to the specific embodiments. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims. 

1. A collapsible chair comprising: upper tubes with lower ends and seat ends, wherein the lower ends have circular cross sections; leg tubes with upper ends; a seat back with tube receptacles; two first short tubes that are bent in U shapes and that are welded to each other at the bottoms of the U shapes, wherein four upper holes with circular circumferences are formed at ends of the first tubes; and two second short tubes that are bent in inverted U shapes and that are welded to each other at the tops of the inverted U shapes, wherein four lower holes with circular circumferences are formed at ends of the second tubes, wherein the first tubes have arms of the U shapes that are welded to arms of the U shapes of the second tubes, wherein the lower ends of the upper tubes are detachably connected to the first tubes by being inserted into the upper holes, wherein the upper ends of the leg tubes are detachably connected to the second tubes by being inserted into the lower holes, wherein the seat ends of the upper tubes are detachably connected to the tube receptacles, and wherein no part of the upper tubes other than the lower ends and the seat ends contacts any part of the collapsible chair.
 2. The collapsible chair of claim 1, wherein the upper tubes consist of two tubes of a first length and two tubes of a second length, and wherein the first length is longer than the second length.
 3. The collapsible chair of claim 2, wherein each of the two tubes of the first length is bent, and wherein neither of the two tubes of the second length is bent.
 4. The collapsible chair of claim 2, wherein each of the upper tubes of the first length has a lower section, a middle section and an upper section, wherein the lower end of each upper tube of the first length is disposed on the lower section of the upper tube, wherein each lower section is curved, and wherein each middle section and each upper section is straight.
 5. The collapsible chair of claim 1, wherein the first tubes are welded to the second tubes at only four locations.
 6. The collapsible chair of claim 1, wherein each of the upper tubes is comprised of detachable sections.
 7. The collapsible chair of claim 1, wherein the circular cross section of each of the lower ends is dimensioned to fit snugly into the circular circumference of a corresponding upper hole.
 8. The collapsible chair of claim 1, wherein the upper tubes consist of four tubes, and wherein the seat ends fit into the tube receptacles at four corners of the seat back.
 9. The collapsible chair of claim 1, wherein the seat back is made of fabric.
 10. The collapsible chair of claim 1, further comprising: an elastic cord that passes through one of the first short bent tubes and into one of the upper tubes.
 11. A collapsible chair comprising: upper tubes with lower ends and seat ends, wherein the lower ends have circular cross sections; leg tubes with upper ends; a seat back with tube receptacles; a central tube connector with two first tubes bent in U shapes and two second tubes bent in inverted U shapes, wherein the first tubes are welded to each other at the bottoms of the U shapes, wherein the second tubes are welded to each other at the tops of the inverted U shapes, wherein four upper holes are formed at ends of the first tubes, wherein four lower holes are formed at ends of the second tubes, wherein arms of the U shapes of the first tubes are welded to arms of the inverted U shapes of the second tubes, wherein the lower ends of the upper tubes are detachably connected to the first tubes by being inserted into the upper holes, wherein the upper ends of the leg tubes are detachably connected to the second tubes by being inserted into the lower holes, wherein the seat ends of the upper tubes are detachably connected to the tube receptacles, and wherein no part of the upper tubes other than the lower ends and the seat ends contacts any part of the collapsible chair.
 12. The collapsible chair of claim 11, further comprising: an elastic cord that passes through one of the upper tubes and into one of the upper holes.
 13. The collapsible chair of claim 11, wherein the four arms of the U shapes of the first tubes are welded to the four arms of the inverted U shapes of the second tubes at four locations.
 14. The collapsible chair of claim 11, wherein the upper tubes include two tubes of a first length and two tubes of a second length, and wherein the first length is longer than the second length.
 15. The collapsible chair of claim 14, wherein each of the two tubes of the first length is bent, and wherein neither of the two tubes of the second length is bent.
 16. The collapsible chair of claim 14, wherein each of the upper tubes of the first length has a lower section, a middle section and an upper section, wherein the lower end of each upper tube of the first length is disposed on the lower section of the upper tube, wherein each lower section is bent, and wherein each middle section and each upper section is not bent.
 17. A method comprising: forming upper tubes with lower ends and seat ends, wherein the upper tubes are formed in sections, and wherein the lower ends have circular cross sections; forming leg tubes with upper ends; bending first tubes and second tubes into U shapes; welding two first tubes to each other at the bottoms of the U shapes, wherein upper holes with circular circumferences are disposed at ends of the first tubes, and wherein the circular cross sections of the lower ends are dimensioned to fit snugly into the circular circumferences of the upper holes; welding two second tubes to each other at the bottoms of the U shapes and inverting the two welded second tubes such that four lower holes with circular circumferences are formed at ends of the second tubes, and wherein the upper ends of the leg tubes are dimensioned to fit snugly into the lower holes; welding arms of the U shapes of the first tubes to arms of the U shapes of the inverted second tubes; and making a seat back with tube receptacles disposed at locations on the seat back so as to fit over the seat ends of the upper tubes.
 18. The method of claim 17, further comprising: pulling an elastic cord through one of the first tubes and into one of the upper tubes.
 19. The method of claim 17, wherein the first tubes are welded to the second tubes at only four locations.
 20. The method of claim 17, further comprising: placing the upper tubes, the leg tubes, the first tubes, the second tubes and the seat back in a bag that is less than one foot long. 21-24. (canceled) 